Atomic radius down group 2

Artist's impression of an atom

Learning outcomes

After studying this page, you should be able to:

  • describe and explain the trend in atomic radius down group 2.

Atomic radius

The table shows atomic radius values for the common elements in group 2.

ElementSymbolAtomic numberAtomic radius /nm

Atomic radius is the distance from the centre of the nucleus to the edge of the surrounding electron cloud. It is measured or calculated in different ways, so values vary from source to source.


The graph shows how atomic radius varies down group 2:

  • as you go down group 2, the atomic radius increases.

When you click on the download symbol, you will be able to download the graph as an image file or pdf file, save its data, annotate it, and print it.


Going down group 2:

  • there are more filled shells between the nucleus and the outer electrons …
  • the outer electrons are more shielded from the attraction of the nucleus …
  • the distance between the nucleus and the outer electrons increases …
  • so the atomic radius increases.

You might expect the atomic radius to decrease because the nuclear charge increases going down the group. However, this does not happen: although the electrons in the inner shells become closer to the nucleus, the factors described in the Explanation have a greater influence overall.